1. Field of the Invention
This invention relates to a recording and/or reproducing apparatus using a rotary head, such as a home video recorder, and more particularly to a rotary transformer arranged in the recording and/or reproducing apparatus to transfer signals between the rotary head and a stationary device.
2. Description of the Related Art
The recording and/or reproducing apparatus of the above-stated kind includes a cylinder device 50 which has a rotary head 52 as shown in FIG. 1. The rotary head 52 is secured to a base 54 and is further secured to a rotary cylinder 56. Information can be recorded and/or reproduced by using the rotary head 52 on or from a magnetic tape which is wrapped around the cylinder device 50. The information is transferred through a rotary transformer 60.
The rotary transformer 60 consists of a stator 60a which is secured to a stationary cylinder 58 on the side of the body of the cylinder device and a rotor 60b which is mounted on the rotary cylinder 56. As shown in FIG. 2, in the conventional rotary transformer 60, each of the stator 60a and the rotor 60b is composed of a core 11.
The core 11 is formed in a disk-like shape with an oxide magnetic substance consisting of ferrite of an Ni-Zn system. A hole 12 is provided in the middle part of the core 11 for inserting a rotary shaft 70 (FIG. 1). A plurality of ring-like winding grooves 13 are arranged concentrically with the hole 12 on a face 11a which is one end face of the core 11 and is opposed to another face. In the case of this illustration, the rotary transformer has two channels. In this case, two winding grooves 13a and 13b are formed, one on the inner circumferential side and the other on the outer circumferential side. Winding 14 is applied to the inside of each of these winding grooves 13. A groove 13' is formed between the winding grooves 13a and 13b. A short-circuit ring 15 is arranged inside the groove 13' to suppress a crosstalk between the two channels.
The core 11 is manufactured, using a Ni-Zn ferrite powder with some binder added, by molding at high pressure, by baking at high temperature and then with some machining process applied as necessary. As mentioned above, the windings 14 (and the short-circuit ring 15) are applied to the inside of the winding grooves 13 (and the groove 13'). A coil to be used for the rotary transformer is made of, for example, a self-welding type copper (Cu) wire which is coated with a polyurethane (PUR) film. The copper wire measures only 0.1 to 0.2 mm. The lead wire end of such a thin wire is not in a fixed shape. The coil of such wire is fixed by means of a suitable adhesive 16.
FIG. 3 shows by way of example the details of an arrangement made at a part of each winding 14 where the wire is pulled out from the core 11. As shown in FIG. 3, the winding 14 is arranged to be pulled out through a hole 17 to one side of the core 11 located opposite to the above-stated opposed face 11a.
The flat type rotary transformer shown in FIG. 2 further includes a terminal 18 and a holder 19 in addition to the core 11. The holder 19 must excel in heat resistivity and moldability. To meet such requirements, the holder 19 is made of a molding material such as a liquid crystal polymer or a PPS (polyphenylene sulfide) resin. The winding 14 pulled out through the hole 17 is wound around a suitable part of the terminal 18. After being wound around the terminal 18 of the holder 19, the winding 14 is fixed by soldering with a solder 20.
The conventional rotary transformer which is arranged in this manner, however, necessitates the thin copper wire to be accurately connected with great care, particularly in processing it at the part where it is to be pulled out (see FIG. 3). This work has been extremely troublesome. Particularly, the recent trend of further reduction in size makes the cementing and soldering work on the winding 14 very difficult. Such work has become impossible without recourse to the manual work of skilled workers. As a result, the ratio of the cost of assembly to the total cost of the product has become much higher than the cost of the part. The cost of assembly thus has been a great impediment to the reduction of cost.
Further, since a high-cost material such as a liquid crystal polymer or PPS resin material is used for the holder 19, the cost of manufacture of the conventional rotary transformer has been increased also by the use of such a material.